High-sensitivity SPECT imaging using large collimator holes and geometric blurring compensation

The low detection efficiency of conventional SPECT results in noisy measurements and degraded image quality. Using large collimator holes improves SPECT detection efficiency with a cost of losing image resolution. This work studies the tradeoff of high-sensitivity SPECT imaging using large collimator holes with geometric blurring compensation. Five types of collimators were investigated and compared with a general all purpose (GAP) Philips AXIS and IRIX SPECT collimator using computer simulations. An "inverse-cone" geometric blurring model is incorporated in the reconstruction. It is shown that less noisy SPECT images can be achieved with the spatial resolution unchanged using large collimator holes with the inverse-cone blurring compensation model. The optimal collimator hole found in the computer simulation is the one with a hole acceptance angle in the range of 6.3deg 9.4deg. In the phantom experiment, a cardiac insert phantom was scanned using a high-resolution collimator and a high-sensitivity collimator with and without blurring compensation, respectively. It shows that the resolution of the image obtained using the high-sensitivity collimator can be successfully recovered by the blurring compensation, and the image is much less noisy compared to the one obtained using the high-resolution collimator.